Demonstrators calling for Beijing to grant full democracy to the former British colony have paralysed parts of Hong Kong, prompting clashes with elements who oppose the blockades and widespread disruption.

Despite repeated orders to disperse, the rallies have taken on an air of permanence, with tents, portable showers and lecture venues -- drawing thousands of people in recent evenings.

In an interview broadcast on local channel TVB Sunday, Leung said the street protests had "spun out of control" and warned it was highly unlikely the action would alter Beijing's position.

After police were criticised for unleashing tear gas on the rallies in late September, the city's chief executive said that if the government had to clear the protests sites, police would use a "minimum amount of force".

China announced in August that while Hong Kongers will be able to vote for Leung's successor in 2017, only two or three vetted candidates will be allowed to stand -- an arrangement the protesters dismiss as "fake democracy".

Since last month students and pro-democracy campaigners have taken to the streets -- sometimes in their tens of thousands -- to call for Beijing to change its position and allow full, free and fair elections and to demand Leung's resignation.

"In achieving universal suffrage in 2017, if the prerequisite is to put down the Basic Law and the decision made by the National People's Congress Standing Committee, I believe we all know that the chance is almost zero," Leung said.

Crunch talks between student leaders and city officials collapsed last week, deepening the crisis in the semi-autonomous city as protesters vowed to dig in for the long haul.

- Heated stand-off -

Demonstrators are occupying three areas of the city. In the districts of Admiralty and Causeway Bay on Hong Kong island many have dug in with food, tents and bedding, as well as displays of artwork, giving the usually busy thoroughfares a carnival feel.

There was a heated stand-off Sunday as a pro-government group marched on Mongkok -- a flashpoint district which has seen ugly scuffles -- with police intervening to keep them apart from the rival activists.

About 200 people took to the streets of the popular shopping hub to call for action to clear the democracy camps, shouting slogans such as "Support police to strictly enforce the law" and "Clear the occupation".

"We want to have a peaceful life. I don't want anybody to occupy Hong Kong. They are making our home a mess," said 63-year-old Stanley Yeung.

"They cannot threaten the central government with a knife at its neck. China is a very powerful country now. Too much freedom and democracy is no good," the retired civil servant told AFP.

In what has become a colour-coded battle, the pro-government Blue Ribbon Movement has threatened to surround the protest sites unless authorities dismantle them by Tuesday night.

Leung was unable to say how the current stalemate between the two sides might end, despite being repeatedly asked for a solution during the television interview.

"We've resorted to all kinds of persuasions, the way we resolve it in the end is being constantly reviewed," he said.

"We absolutely would not prefer clearing the venue, but if one day the venue has to be cleared, I believe the police will use their professional judgement and training using minimum amount of force," he said.

Leung reiterated his insistence that he will not resign, saying it would not resolve the situation.